White smoke usually means burning oil. However, over the past two years I've seen a few healthy engines smoking from bad fuel. The exhaust stream looked like the motor was inhaling antifreeze through a failed headgasket...more than weird on an air cooled engine:43:. Draining the "panther piss" & refilling the tank with fresh gas solved the problem.
Check the spark plug for signs of oil fouling. If there are none, you're probably alright. If the plug is oiled, you're going to have to figure out where the oil is entering the combustion chamber. 150 miles ought to be sufficient to seat the rings, though the motor will still be tight.